Patent GB-408948-A (GB)
Title: Improvements in process for production of lubricating oil
IPC: C10G21/02
Filed: 1932-07-11
Abstract: <PICT:0408948/III/1> Lubricating-oils are obtained by mixing a lubricating-oil fraction with a liquefied normally gaseous hydrocarbon diluent, removing non-paraffinic constituents from the resulting solution by extraction with a solvent, and removing the diluent and solvent from the resulting paraffinic lubricating oil. The gaseous hydrocarbon used is preferably a fraction obtained from natural gasoline, consisting mainly of propane.  Non-paraffinic solvents specified are liquefied sulphur dioxide, aniline, methyl formate, acetone or a mixture of acetone and benzol.  A lubricating oil distillate containing asphalt and wax and free from light oils, passes from a tank 1 through a pipe 4 in which it is mixed with liquefied propane and flows into a chiller 5 where a portion of the propane is vaporized to lower the temperature of the mixture. The cooled mixture passes through an agitator 14 to a decanter 16 in which asphalt is precipitated.  The asphalt is withdrawn and flows through a heater 20, in which propane is evaporated and recovered, and through a separator 22 to a tank 25.  The solution of oil in propane passes from the decanter 16 and flows into a chamber 34 where a further amount of propane is vaporized to chill the mixture.  The cooled mixture is then introduced into the base of an extraction column 41, at the top of which liquefied sulphur dioxide is admitted from a tank 42.  The two liquids flow in counter current and the sulphur dioxide and extracted substances flow into an evaporator 105 provided with a steam coil, in which sulphur dioxide is driven off and recovered, and the oil extract is drawn off into a tank 104.  The ascending stream of purified oil in the extraction column 41 passes through a separator 50 in which the bulk of the sulphur dioxide is removed, and is then mixed with liquefied propane and admitted to a chiller 55.  By treating the oil with sulphur dioxide prior to dewaxing, wax solvents are removed and dewaxing is facilitated.  A portion of the propane is allowed to evaporate to precipitate the wax and the resulting vapours containing some sulphur dioxide are compressed and pass to a separator 90 from which propane and sulphur dioxide are separately returned to their separate tanks.  The solution of oil in propane and precipitated wax passes from the chiller to a dewaxing stage 59 consisting of a centrifuge, filter or settling chamber.  The wax-free oil flows from the dewaxing stage and passes in admixture with sulphuric acid admitted from a tank 63, through an agitator 68 into a sludge separator 70.  The sludge is withdrawn through a pipe 76 and passes through a heater 79 in which propane is recovered, into a separator 81 and finally to a tank 84. The solution of acid treated oil in propane in the separator 70 passes through a tower 72 containing clay and then into a steam-heated evaporator 74 in which vapours of propane and sulphur dioxide are driven off, condensed, separated in the gravity separator 90 and separately recovered.  The refined paraffinic lubricating oil passes finally from the evaporator into a tank 100.